Pope Francis celebrates Mass with bishops, priests and seminarians at the Cathedral of St. Sebastian in Rio de Janeiro on Saturday. / Luca Zennaro, AFP/Getty Images

by David Agren, Special for USA TODAY

by David Agren, Special for USA TODAY

RIO DE JANEIRO - An estimated three million Catholics crammed onto the iconic Copacabana Beach Saturday night for a vigil with Pope Francis, whose visit to Brazil culminates tomorrow with a Mass that is expected to convene an even bigger crowd.

The vigil capped a busy day for Francis, who arrived in Brazil July 22 for World Youth Day, a biannual gathering of young Catholics.

Earlier on Saturday, Francis told an assembly of Catholic bishops in the cathedral of Rio de Janeiro to get out of their cathedrals and spread the gospel and serve those most in need.

It was yet another admonishment from the first Latin American pontiff - who has called for a Church focused on the poor - for Catholics to adopt a more missionary mind-set. It also blasted bishops from Brazil, where the number of faithful has shrunk to less than 65% of the population in what is still the world's most Catholic country.

"We cannot keep ourselves shut up in parishes, in our communities, when so many people are waiting for the Gospel," Francis said.

"Let us courageously look to pastoral needs, beginning on the periphery (of where we live), with those who are farthest away, with those who do not usually go to church. They, too, are invited to the table of the Lord."

It was message aimed at reviving an institution dating back centuries in Latin America, but one becoming less relevant in the region as people become culturally Catholic or leave the church all together - often for Evangelical congregations. Those congregations have often better identified basic needs in poor Brazilian neighbourhoods and addressed issues like domestic violence and alcohol abuse, instead of speaking about more global ideas like social justice, says Andrew Chesnut, religious studies at Virginia Commonwealth University and the author of a book on Brazil's Evangelicals

Papal spokesman Father Federico Lombardi said the speech to the bishops was the longest of his pontificate and outlines his vision for them, Catholic News Service reported.

The pope later took his straight-talking style to a speech for intellectuals and Brazil's political and business leaders. He implored them to open opportunities for everyone in a country rife with inequality, expand dialogue with all sectors of society and work toward "eliminating forms of elitism and eradicating poverty."

Brazil has been beset by demonstrations over protesters' complaints of an unresponsive political class, police repression and irresponsible spending on sports stadiums for the 2014 World Cup and 2016 Olympics - while infrastructure remains inadequate and the health and school systems provide poor service.

Francis called for "social humility" and dialogue without directly mentioning the protests.

"When leaders in various fields ask me for advice, my response is always the same: dialogue, dialogue, dialogue," he said. "It is the only way for individuals, families and societies to grow, the only way for the life of peoples to progress."

Francis frequently criticized corruption and the political class in his native Argentina, especially the populist politics of President Cristina FernÃ¡ndez de Kirchner and politicians forming patronage groups among the poor.

"Politicians hated him, but people love him," said Marina Artese, 23, a schoolteacher from Buenos Aires.

Looking to the wider world, he added, "Peaceful coexistence between different religions is favored by the secularism of the state."

For young people, their Saturday focus was on faith. Many made pilgrimages by walking to the Copacabana Beach.

Once there, they staked out spots on the sand. Some slept, played soccer and build sandcastles under sunny skies as they waited for the pope to arrive for what was to be a solemn event.

"It's a true experience of faith," said Chris Whitson, who help chaperon a group of 86 youths from Georgia and the Carolinas.

"I hope that youth take away the courage to live their faith in a more concrete way," said Jose Luis Hernandez, a priest from Atlanta.

"The community of young people from around the world," said Francisca Martinez, 21, a student from Guam.

"To have something in common helps (overcome) the language barriers."

Many young people planned to camp on the beach Saturday night, pitching tents and spreading out sleeping bags to sleep under the stars. Organizers asked those doing so to donate their sleeping bags afterward to the homeless.

On Friday night, Francis issued an impassioned plea for the downtrodden and oppressed while addressing throngs of young Catholics on Copacabana Beach for a re-enactment of Christ going to his crucifixion.